A wide gamut of colors can be generated and displayed by intermixing red, green, and blue primary light sources in different ratios. In general, a color that matches any particular color sample can be produced on a display using the three primary colors.
However, the ratios of the red, green, and blue primaries that produce a color that matches any particular sample depend on the ambient light used to illuminate the color sample. Moreover, when only the three primary colors are used, it is possible to produce a color that some people see as a match to a sample, but that other people see as a mismatch. Colors that look alike in some ambient illuminations look different in other illuminations, and colors that look alike to some people look different to others. These phenomena are referred to as "metamerism".
Appearance of the color under given illumination depends on both the reflectance spectrum and the illuminance spectrum. Consequently, reproduction of the appearance of a color sample requires knowledge of both the complete reflectance spectrum and the complete illuminance spectrum. When these are known, the color can be reproduced by generating the spectrum that is the convolution of these two.
Perfect reproduction of a color requires control over the intensity level of each wavelength of the visible spectrum. In practice, the spectrum can be divided into a plurality of bands, and the average intensity within each band can be specified. Using four or five such bands results in significantly reduced metamerism, compared with the commonly used three primary colors. Using seven bands reduces the metameric effects by an order of magnitude. Therefore, a need exists for a system for specifying, measuring, displaying, and communicating colors with reduced metameric confusion.